Done?

Assets/Scripts/GameManager.cs

@@ -1,6 +1,7 @@
 using System;
 using UnityEngine;
 using Level;
+using Objects;
 
 public enum GameState
 {
@@ -21,6 +22,7 @@ public class GameManager : MonoBehaviour
     public GameState currentState { get; private set; } = GameState.Editing;
 
     // Private
+    [SerializeField] private GameplayUI gameplayUI;
     private LevelData currentLevelData;
 
     // Properties
@@ -35,10 +37,17 @@ public class GameManager : MonoBehaviour
             Destroy(gameObject);
             return;
         }
+
         instance = this;
     }
 
 
+    private void Start()
+    {
+        Player.Instance.PlayerMoved += CheckWin;
+    }
+
+
     // Used by button OnClick
     public void SetPlayState()
     {
@@ -61,4 +70,13 @@ public class GameManager : MonoBehaviour
 
         GameStateChanged?.Invoke(currentState);
     }
+
+
+    private void CheckWin()
+    {
+        if (!LevelBuilder.Instance.UnoccupiedTargetExists())
+        {
+            gameplayUI.ShowWinScreen();
+        }
+    }
 }